Peripherally inserted central catheter with continuous central venous oximetry and proximal high flow port

ABSTRACT

A peripherally inserted central catheter includes three lumens that communicate with its proximal end. A large lumen terminates short of the distal end of the catheter and is used for the infusion of fluids into the venous system. A second lumen terminates at the distal end and is suitable for measuring blood pressure in the central venous system and infusion of fluids into the central venous system. The third lumen houses a pair of optical fibers which form part of a central venous oxygen saturation (SvO 2 ) monitoring system.

BACKGROUND OF THE INVENTION

[0001] The field of the invention is catheters, and in particularcatheters inserted into the central venous system.

[0002] Oxygen is essential to human life. An immediate cascade ofpathologic processes is triggered in response to a decrease in oxygendelivery. Since oxygen is not stored in sufficient quantities in thebody, inadequate oxygen transport to the cells for even very briefperiods of time can result in organ failure and death. Thus our abilityto monitor and increase oxygen delivery to the body is essential topreventing and reversing organ dysfunction (such as heart, kidney andliver failure or coma) and death. The goal is to balance oxygen supplywith tissue oxygen demand.

[0003] In an effort to properly balance oxygen supply and demand anumber of measurements are commonly made. Current monitoring techniquesinclude continuous electrocardiographic monitoring, measurement of bloodpressure, measurement of skin temperature and capillary refill. Thesenoninvasive techniques provide little information regarding hemodynamicstatus and/or oxygen delivery to the brain or body (tissue).

[0004] Mixed venous oxygen saturation (SvO₂) is the amount of oxygen inblood taken from a vessel coming from the right side of the heart goinginto the lungs. This reflects the amount of oxygen being delivered tothe tissues. When oxygen delivery to the tissues is inadequate, the SvO₂is low. When oxygen delivery to the tissues is adequate, the SvO₂ isnormal or high. This is the physiological basis for using SvO₂ as theearliest indicator of response to therapy during patient treatment.

[0005] Ideally, SvO₂ is drawn from a pulmonary artery catheter which isapproximately 100 centimeters long and is placed into a vein thataccesses the right side of the heart and then into the pulmonary artery.However, placement of a pulmonary artery catheter is extremely difficultand can be impractical during cardiac arrest and severe shock due to lowblood pressure and may actually increase patient mortality.

[0006] The central venous system avoids traversing the heart and can bemore easily accessed. Thus, a number of studies have supported thesubstitution of central venous (right atrial or superior vena cava)oxygen saturation (ScvO₂) for pulmonary artery blood oxygen saturation(SvO₂). The central venous blood can be obtained much more easily thanblood from the pulmonary artery because the heart does not need to betraversed.

[0007] Central venous measurement of oxygen saturation (SvO₂) iscurrently achieved by puncture of the central venous circulation (CVC)system (i.e., internal jugular vein, subclavian vein or femoral vein)and insertion of an intravascular catheter device such as that disclosedin U.S. Pat. No. 5,673,694. Such CVC catheters employ fiber optics tomeasure SvO₂ as described, for example, in U.S. Pat. Nos. 5,754,716 and4,711,522. They are relatively short (i.e., less than 30 cm in length)and inflexible devices which can remain in place for only a short time(e.g., generally less than 7 days).

[0008] The use of CVC catheters to measure oxygen saturation and bloodpressure from the superior vena cava or right atrium has a number ofdrawbacks. These CVC catheter insertions are known to be associated withcomplications of lung puncture (pneumothorax), major hemorrhage, neckhematoma, carotid artery puncture, cardiac dysrhythmias and infection.In addition, because they can remain in place for only a short time,repeated insertions are necessary when monitoring is required over along time period.

[0009] Peripherally inserted central venous catheters have beenavailable for many years to administer fluids such as parenteralnutrition, chemotherapy, vasopressor (adrenalin like medications),antibiotics and other hypertonic/caustic solutions. These catheters arealso used for blood draws. These catheters are inserted into peripheralveins (generally the antecubital, basilic or cephalic veins) andadvanced into the central (deep) venous system with the tip ideallypositioned in the superior vena cava or right atrium thus allowing fordilution of infused fluids.

[0010] The use of such peripheral catheters avoids the complicationsassociated with the direct puncture of the central venous circulationsystem and they can remain in place for extended periods of time.However, due to their longer length, smaller diameter and greaterflexibility, peripheral catheters have not been used for rapid infusionmeasurement of central venous blood pressure or continuous centralvenous oximetry.

SUMMARY OF THE INVENTION

[0011] The present invention is a multilumen catheter which can beinserted via a superficial (peripheral) vein into the central venoussystem for drug infusion, phlebotomy, rapid fluid infusion, hemodynamicpressure monitoring and central venous oxygen saturation monitoring.More specifically, the catheter includes a sheath having a length anddiameter suitable for extending from a peripheral vein insertion pointto the superior vena cava of the patient and having two lumens formedtherein which extend from its proximal to its distal ends. A pair ofoptical fiber cables extend through one lumen and connect to an oxygensaturation measurement instrument at the proximal end, and a medicalinstrument such as a blood pressure monitor connects to the proximal endof the other lumen.

[0012] One object of the invention is to monitor central venous oxygensaturation using a peripherally inserted catheter. The peripheralinsertion results in the need for a substantially longer and moreflexible sheath while at the same time providing protection for thedelicate optical fibers used by the oxygen saturation measurementinstrument.

[0013] Another object is to provide a peripherally inserted catheterwhich enables simultaneous measurement of central venous blood pressureand oxygen saturation. One lumen houses the optical fibers needed foroxygen saturation measurement, and the other lumen may be employed tomonitor blood pressure in the central venous system.

[0014] Another aspect of the invention is the addition of a third lumenin the sheath which has a size sufficient to rapidly infuse fluids. Flowrate is increased by terminating the third lumen at a port in the sheathlocated at a point intermediate its ends. The port is located withrespect to the distal end of the sheath such that fluid flows into orproximal to the subclavian vein when the distal end of the sheath ispositioned in the superior vena cava.

[0015] The foregoing and other objects and advantages of the inventionwill appear from the following description. In the description,reference is made to the accompanying drawings which form a part hereof,and in which there is shown by way of illustration a preferredembodiment of the invention. Such embodiment does not necessarilyrepresent the full scope of the invention, however, and reference ismade therefore to the claims and herein for interpreting the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a partial pictorial view of the venous system of a humansubject;

[0017]FIG. 2 is a pictorial view of the preferred embodiment of theperipheral catheter which employs the present invention;

[0018]FIG. 3 is a cross-sectional view of the catheter along the planeindicated at 3 in FIG. 2;

[0019]FIG. 4 is a cross-sectional view of the catheter along the planeindicated at 4 in FIG. 2;

[0020]FIG. 5 is a cross-sectional view of the catheter along the planeindicated at 5 in FIG. 2; and

[0021]FIG. 6 is a partial view in cross-section of the distal end of thecatheters of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] Referring particularly to FIG. 1, the catheter 10 of the presentinvention is inserted into a superficial, or peripheral vein of apatient. The central venous system is comprised of the superior venacava 12 which extends downward into the right atrium of the heart (notshown in the drawings) and a set of veins which connect to it. Thesecentral venous system veins include the internal jugular vein 14, thesubclavian vein 18, the axillary vein 20 and brachial vein 24.

[0023] These central venous system veins lie deep beneath subcutaneoustissue and accompany large arteries. They are supplied with blood from anetwork of smaller, peripheral veins that extend throughout the limb ofthe patient and are located just under the skin (hence the term“superficial” veins). In the arm shown in FIG. 1, these peripheral veinsinclude the cephalic vein 22, the basilic vein 26 and cubital vein 28 inthe upper arm as well as the radial vein 30 and ulnar vein 32 in thelower arm. Some of these peripheral veins are better than others forinsertion of a catheter. Unlike the cephalic vein, the basilic vein doesnot collapse or kink with flexion of the deltoid and pectoral muscles,and is of larger caliber, providing a more favorable vein-to-catheterratio. Avoiding distal and intracubital placement improves patientperception of mobility for activities of daily living and avertscatheter “kinking” with arm flexion.

[0024] There are two requirements of a peripherally inserted centralcatheter which distinguish it from a central venous circulation (CVC)catheter. First, it is much longer. The distance from the superior venacava 12 from a typical subclavian insertion point is only 15 cm, whereasthe distance from a peripheral insertion point such as cephalic vein,basilic vein or cubital vein is from 40 to 60 cm.

[0025] The second major distinction is that the peripherally insertedcatheter must have more flexibility than a CVC catheter. The CVCcatheter has a relatively short, straight run to the superior vena cava,whereas the peripheral catheter has a longer, more tortuous path. Inaddition, the peripheral veins are smaller in size and not as rigidlyanchored in place. Flexibility is required, therefore, in order toeasily wind the peripheral catheter through the smaller, compliantperipheral veins.

[0026] The preferred embodiment of a peripherally inserted centralcatheter 10 is shown in FIG. 2 and includes a sheath 50 made of apolyurethane base polymer. It has a diameter of 5.0 to 5.3 French at itsproximal end 52 and is tapered to a smaller diameter at its distal end54. The sheath 50 is 55 cm in length and it has a radiopaque strip (notshown) along its entire length for visualization with x-ray imagingsystems. Polyurethane offers many advantages over other materials forthe sheath 50. Polyurethane is a more durable material enabling the useof thinner lumen walls. It offers less friction for ease of insertion;it is biocompatible; it has good tensile properties for safe insertionwithout kinks or fractures; it is resistant to hydrolysis, oxidation,oils and thermal degradation; it is thromboresistant and non-hemolytic;and it is rigid at room temperature but softer at body temperature tobecome more pliant, flexible and kink resistant when inserted into avein. It also allows better transduction of pressures than othermaterials.

[0027] Referring particularly to FIGS. 2 and 3, the first 30 cm of thecatheter 10 as measured from its proximal end 52 encloses three lumens60, 62 and 64. The lumens 60, 62 and 64 are formed by walls 66integrally molded on the interior of the sheath 50. The lumen 62 is thesmallest in size and it is substantially centered inside the sheath 50.It houses two optical fiber cables 70 and 72 which extend the entirelength of the catheter 10 as will be described in more detail below. Thewall 66 surrounding lumen 62 must be of sufficient thickness to protectthe delicate optical fibers 70 and 72 and prevent them from kinking whenthe catheter is being inserted.

[0028] The lumen 64 is a 20 gauge lumen which also runs the entirelength of the catheter 10, and as will be described below, it may beused for measuring blood pressure, drawing blood, infusing drugs, andguidewire housing during insertion of the catheter 10.

[0029] The lumen 60 is the largest lumen in the sheath 50. It is 17gauge and it extends from the proximal end 52 of the sheath 50 to anopening, or port, 80 in the sheath 50 located 30 cm from the proximalend 52. It is thus located 25 cm from the distal end 54, and when thecatheter 10 is fully inserted with its distal end 54 located in thesuperior vena cava 12, the port 80 is positioned within or proximal thesubclavian vein 18. The large lumen 60 which the port 80 terminates thusprovides a pathway for the infusion of fluids at a relatively high flowrate into the central venous system. Port 80 has a slit valve such asthat disclosed in U.S. Pat. No. 5,810,789 and sold by C R Bard Inc.under the trademark “Groshong® valve”. The Groshong® valve opens inwardfor blood aspiration and outward for infusion but remains closed whennot in use. Because the valve remains closed when not in use, it sealsthe fluid inside the catheter and prevents it from coming in contactwith the patient's blood. This closed ended system provided by the slitvalve reduces the risk of blood reflux and air embolism. By maximizingthe size of the lumen 60, increasing the size of the opening 80 andshortening the total length of the lumen 60 (i.e., 30 cm instead of 55cm) a dramatic increase in fluid flow rate is achieved. In accordancewith Poiseuille's Law:

Q=r ⁴ ΔP/8ηL

[0030] where: Q=flow

[0031] r=internal lumen radius

[0032] ΔP=change in pressure

[0033] L=lumen length

[0034] η=constant.

[0035] Referring particularly to FIGS. 2 and 4, immediately distal thelumen opening 80 the internal configuration of the lumens housed by thesheath 50 changes. The lumen 60 is no longer present, but the lumens 62and 64 continue on undisturbed. The outer diameter of the sheath 50 isalso unchanged at this point, but it gradually decreases in size as oneprogresses toward the distal end 54.

[0036] As shown best in FIGS. 2 and 5, at the distal end 54 of thesheath 50, the two lumens 62 and 64 terminate at openings in the tip ofthe catheter 10. The ends of the optical fiber cables 70 and 72 areexposed at the tip in a manner such as that disclosed in U.S. Pat. No.5,196,004 so that light may be transported from the proximal end 52 inone optical fiber cable 70 to blood surrounding the catheter tip 54 andreflected light may be transported back to the proximal end 52 throughthe other optical fiber cable 72. As will be described below, thisoptical information is used to monitor central venous oxygen saturation.The lumen 64 extends through the distal end 54 and a port 65 is formedto communicate with surrounding blood as shown in FIG. 6. The outerdiameter of the sheath 50 is reduced substantially at the distal end 54to enhance the flexibility of the catheter and facilitate its insertion.

[0037] Referring particularly to FIG. 2, the three lumens 60, 62 and 64are terminated at the proximal end 52 of the sheath 50 by a cathetermanifold 90 such as that disclosed in U.S. Pat. No. 4,670,009 which isincorporated herein by reference. The catheter manifold 90 connects thelumens 60, 62 and 64 to respective catheter extension tubes 92, 94 and96. The optical fiber cables 70 and 72 extend into the catheterextension tube 94 and terminate in a connector portion of aconnector/receptacle 98 such as that described in U.S. Pat. No.5,007,704 which is incorporated herein by reference. The receptacleportion of the connector/receptacle 98 forms part of an oxygensaturation measurement instrument 100 such as that described in U.S.Pat. No. 4,651,741 which is also incorporated herein by reference. Theoxygen saturation instrument 100 measures oxygen saturation in bloodflowing past the distal tip of the catheter 10 by detecting the relativereflectivity of the blood under red illumination and infraredillumination. The intensity signal λ₁ of red light reflected by bloodback through optical fiber cable 72 is measured, as is the intensitysignal λ₂ of the reflected infrared light. The intensity ratio I=λ₂/λ₁is used to calculate oxygen saturation of the blood.

[0038] The catheter extension tubes 92 and 96 are terminated withconnectors 102 and 104 which enable them to be connected to a number ofdifferent devices. Connector 102 is shown connected to a syringe 108.The syringe may be operated to infuse at a high flow rate a fluidthrough the large catheter lumen 60 to opening 80 aligned within orproximal to the subclavian vein 18. Such fluids might be, for example,resuscitation crystalloid, colloids, blood products or intravenouscontrast.

[0039] The connector 104 is shown connected to a blood pressure monitorinstrument 110. An instrument 110 such as that commercially availablefrom Maxxim, Inc. under the trade name “CDXpress® transducer” may beused for this purpose. This is a continuous infusion transducer devicein which a low constant flow of saline solution, or heparinized salinesolution is pumped through the lumen 64 and out its distal opening atthe tip of the catheter 10. A flow rate of 3 mL/hr is all that isrequired to flush the lumen 64 and insure that the blood pressure at thetip of the catheter 10 is accurately reflected through the lumen 64 to apressure transducer (not shown) in the monitor 110.

[0040] Referring particularly to FIGS. 1 and 2, the catheter 10 isinserted in the patient through a peripheral vein in the arm (e.g.,basilic, cephalic or cubital veins). A 1.88″, 20 Gauge intravenouscatheter is inserted in the peripheral vein and a 30 cm long, 0.018″diameter spring guidewire is passed through the intravenous catheterleading to the central venous system. The intravenous catheter is thenremoved and a 5.0-5.5 French sheath introducer and dilator unit (e.g.,such as that sold by HDC Corporation under the trademark V=cathSafe-T-Peel”® or that sold by Cook Critical Care under the trademarkPeel-Away Cook®) is inserted over the guidewire. The guidewire anddilator are removed leaving the introducer in the peripheral vein. Thecatheter 10 is then inserted through the introducer and guided into thecentral venous circulation terminating in the superior vena cava. Asshown in FIG. 6, the catheter 10 is preloaded with a 0.025″ diameterremovable guidewire 112 that passes through connector 104, extension 96and lumen 64 terminating proximal the catheter tip 54. The guidewire 112provides increased catheter stiffness during the insertion process. Theintroducer sheath is split and peeled away from the catheter 10 onceinsertion is complete. Upon confirmation of catheter position with achest X-ray, the preloaded removable guidewire 112 is withdraw andconnector 104 is fastened to the pressure monitor 110. A securing devicesuch as that sold by Arrow International under the trademark “Statlock®”may be used at the insertion site to prevent catheter dislodgement ormigration.

[0041] When fully inserted the catheter 10 may be used to perform anumber of functions. The central venous oxygen saturation (S_(cv)O₂) ismonitored by instrument 100 and the venous blood pressure is monitoredby instrument 110. Any fluids that need to be introduced into thecentral venous system may be injected using syringe 108 or an infusionpump (not shown in drawing). Because of its peripheral insertion, thecatheter 10 may remain in place and fully functional for months.

[0042] It should be apparent that variations in the preferred embodimentdescribed above are possible without departing from the spirit of theinvention. For example, 55 cm is an optimal length for the peripheralcatheter for insertion in the best peripheral veins in the upper arm,but lengths ranging from 35 cm to 65 cm are useful for peripheralinsertion. Similarly, a range of sheath diameters are possible, but forperipheral insertion the diameter should not exceed 5.5 French. Also,other devices can be connected to and use the two lumens 60 and 64. Forexample, infusion pumps, radiocontrast power injectors, and pressurebags for lumen 60 and syringes or infusion pumps for lumen 64. Also,while in most procedures it is sufficient to extend the distal tip ofthe catheter into the superior vena cava, it will be understood by thoseskilled in the art that the catheter tip may also be extended into theright atrium of the patient's heart. Structurally, no changes in thecatheter are required to do this, although another 5 to 10 cm of lengthmay be helpful.

1. A peripherally inserted central venous system catheter whichcomprises: a sheath having a length and a diameter suitable forextending from a peripheral vein insertion point on a patent to thesuperior vena cava of the patient, the sheath being constructed of amaterial suitable for insertion into the venous system of a subjectthrough a peripheral vein and forming two lumens therein which extendfrom its proximal end at the insertion point to its distal end in thesuperior vena cava; a pair of optical fiber cables disposed in one ofthe lumens and extending from the distal end to the proximal end of thesheath; a connector fastened to the proximal ends of the two opticalfiber cables for connecting them to an oxygen saturation measurementinstrument; and a second connector fastened to the proximal end of theother of said two lumens for connecting the second lumen to a medicalinstrument, wherein central venous oxygen saturation of the patient'sblood is measured and a medical procedure is simultaneously performedusing the medical instrument.
 2. The catheter of claim 1 in which themedical instrument is a blood pressure monitor which measures bloodpressure at the distal end of the sheath.
 3. The catheter as recited inclaim 1 in which the sheath has a length greater than 35 cm.
 4. Thecatheter as recited in claim 3 in which the sheath has a diameter lessthan 5.5 French.
 5. The catheter as recited in claim 1 in which thesheath is formed from a polyurethane base polymer.
 6. The catheter asrecited in claim 1 in which a third lumen is formed in the sheath andextends from its proximal end to a point intermediate the ends of thesheath where it communicates with blood surrounding the sheath through aport formed in the sheath; and a third connector is fastened to theproximal end of the third lumen for connecting the third lumen to afluid infusion device; wherein the third lumen is larger than said twolumens such that fluids may be infused into the central venous system ofthe patient through said port.
 7. The catheter of claim 6 in which themedical instrument is a blood pressure monitor which measures bloodpressure at the distal end of the sheath.
 8. The catheter as recited inclaim 6 in which the sheath has a length greater than 35 cm.
 9. Thecatheter as recited in claim 8 in which the sheath has a diameter lessthan 5.5 French.
 10. The catheter as recited in claim 6 in which thesheath is formed from a polyurethane base polymer.